Thanks but I solved this problem with this tip:Re: Error when trying to copy one of my folders, or compress it in the finder
I found some subdirectories within my Project folder that were complete duplicates of other directories. After deleting those, I no longer had the error. I don't know where they came from, but think they may have been created after an upgrade, say from Xcode 3.0 to 4.0 but don't remember. Anyway, don't know any more about it, only that it went away after I deleted those duplicate subfolders. Good luck !
I found unlimited folder in folder in my Xcode project folder that made the size from 285MB to 1.5G. It was that duplicate folders made this error.
I removed and it solved the problem.